DLR signs cooperation agreement to investigate alternative fuel types for use in aviation

13 October 2009

The Airbus A340-600 from Qatar Airways

The first scheduled commercial flight to use synthetic fuel

No dependency on oil: this is the objective of the five research partners who, on Tuesday, 13 October 2009 in Doha, Qatar, signed a cooperation agreement to investigate alternative fuels for use in aviation. Together with the energy company Shell, the technology centre Qatar Science & Technology Park (QSTP), Texas A&M University at Qatar and the engine manufacturer Rolls Royce plc, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) will study the use of synthetic fuels that are based on natural gas in a three-year research project.

The first scheduled commercial flight of an Airbus A340-600 from Qatar Airways using GtL (Gas to Liquid) fuel, a high-performance synthetic fuel that is based on natural gas, took off from London Gatwick at 10:15 on 12 October, bound for Qatar. This marked the first time that a regular scheduled flight carrying passengers has used a fuel that is made up of 50 percent GtL synthetic fuel and 50 percent kerosene.

A bridge to 'biofuels'

"The development of GtL fuel is an important step in two directions with respect to aviation," said Prof. Manfred Aigner, Director of DLR’s Institute of Combustion Technology. "Together with our partners, we will get to know the characteristics of the new generation of fuel types, develop the necessary tools and thus build an important bridge to 'biofuels', renewable energy sources that are based on biomass. At the same time we will be decreasing our reliance on crude oil with the goal of using totally synthetic fuels in flight," says Prof. Aigner. The resulting lack of dependence on oil will allow the increasing volume of air traffic to continue on its growth path in the future, and means that the use of BtL fuels (biomass to liquid) will soon be attainable.

High-velocity burner used in flame characterisation

The synthetic gas-to-liquid fuel is a crucial first step toward the use of alternative fuels in aviation. It is created using the 'Fischer-Tropsch method', named after its inventors, in which natural gas is first converted into a synthetic gas by adding oxygen and water vapour and then to liquid hydrocarbons. The plan is to produce commercial quantities of around one million tons of GtL fuel per year, starting in 2012, in Qatar under the auspices of Shell and Qatar Petroleum. Three research projects have been created within the framework of this investment.

Analysing the characteristics of GtL fuel

In the research project for characterising the combustion characteristics of GtL fuel, the partners will, over a three-year period, improve the new fuel with respect to polluting emissions and performance. DLR's Institute of Combustion Technology in Stuttgart is responsible for analysing the combustion processes and characteristics of the new fuel mixture. The GtL fuel must fulfil well over 50 different criteria to be permitted for use as an aviation fuel - for example, with respect to the ignition point, the tendency to form soot, or the freezing point (the synthetic jet fuel must remain liquid even at ambient air temperatures of minus 47 degrees Celsius). In order to be able to determine all of these characteristics, DLR's scientists will draw on their decades of experience in the area of combustion research and their many years of experience in the field of alternative fuels in particular.

The combustion specialists from DLR will first analyse the GtL fuel – which has already been manufactured by Shell and certified for use in aviation and is now to be optimised - on the combustion test benches in Stuttgart, using various measuring techniques. Taking the measured data from the bench tests, as a next step they develop complex physical and chemical computer models for combustion in aircraft gas turbines, which map the various characteristics of the synthetic fuel. These models will then make it possible to test existing fuels. At the same time they facilitate a crucial steps forwards: a future fuel can be optimised in advance, in a targeted design process. This is particularly interesting for synthetic fuels such as GtL, whose composition can be adjusted as required.

Interdisciplinary combustion research in Stuttgart

With its test bench infrastructure in combination with its competence in the areas of pollutant analysis, measuring technology, modelling of combustion processes, and chemical kinetics, which, for example, studies the ignition behaviour, the flame speed and the release of heat, to computer simulation, DLR's Institute of Combustion Technology in Stuttgart offers a comprehensive approach for determining the optimum future fuel for use in aviation.